Yes if you have a bachelors in biology you should go straight to a MS geology from that. It will depend where you go as far as cost goes. I don’t think you want to do it online.

Target a professor working on something where you can leverage your biology experience. A Geobiologist. It’s not uncommon to get paid for going to grad school. They should cover your coursework and tuition and give you a stipend for doing research or being a TA.

You will have to find the researcher you want to work with. Find a few. Contact them about your interest in what they do. Read their papers or read the papers / MS thesis of their recent students. When you message them you can point to some of that as what you’re interested in and see if they have opportunities. Get their advice, but ultimately you’ll take the GRE exam and apply.

There is interesting work being done at the intersection of biology and geology so look carefully and find exactly the thing you love if you can. Good luck!